Marine Engine Cooling Water Systems
There are various seawater cooling systems which use different numbers of coolers in different locations. We shall examine below these systems.
1. Direct seawater cooling
This was the established system for as long as I can remember and although still in use on older ships, is being phased out.
In this system the major components of the engine have their own coolers; oil, jackets, pistons, turbo blowers and fuel injectors, cooled by the seawater cooling pumps.
The main advantages are that the system is easy to control and is the least expensive to install. However the length of pipework along with the number of coolers increases the amount of internal biofouling from seawater circulation.
I well remember as a junior engineer running around the numerous coolers and adjusting the seawater inlet valves to regulate temperatures during main diesel engine maneuvering leaving and entering port.
2. Central Cooling using one cooler
This is now the preferred system, using one large central plate cooler to cool the jacket water. This cooled jacket water is used as the medium to cool the engine oil and turbo-blower air instead of seawater. An evaporator can be added to the circuit, using the jacket cooling water to heat the seawater, which is directed from the central cooler.
The advantage of this system is that there are fewer coolers and less piping exposed to seawater, however temperature control is more difficult and if pistons are water cooled, they will need a dedicated cooler as in described the next system.
3. Central Cooling using two coolers
This system is similar to the central cooling system, with the addition of a dedicated piston water cooler, retaining some of the advantages of the previous system. However, the plates in this cooler will have to be of stainless or titanium as they are exposed to seawater, and more seawater system piping will be required.
Reference Web: geaphe - ships engine cooling systems